1. The Field of the Invention
This invention relates to valves used to control the flow of a liquid through a pipe. More particularly, the present invention relates to devices used to remotely and/or automatically operate irrigation valves.
2. The Background Art
In many parts of the world, and particularly in the Western United States, the efficient production of agricultural products requires that the natural rainfall be supplemented with irrigation water. Many times such irrigation water travels long distances from far away reservoirs and rivers to arrive at the farmer's fields.
Irrigation systems began to be used in the Western U.S. in the late 19th century. Such early irrigation systems generally consisted of a series of canals and ditches which were capable of transporting water from a reservoir or river to adjacent the farmer's field. The water would then be diverted from the canal or ditch down the furrows between the crops in the field. Since the early implementation of irrigation, irrigation systems have become much more sophisticated.
Many current irrigation systems are comprised of complex systems of pipes which carry water pumped from a canal, underground aquifer, or other source to the field. The main pipes used in modern irrigation systems may be twelve inches in diameter and carry 1,000 gallons or more of water per minute.
Rather than direct the water down the furrows, modern irrigation systems generally employ sprinklers to efficiently disperse the water among the crops. It is common for such sprinklers to be mounted above the crops on a wheeled structure which moves through the field. Some sprinkling systems include many sprinkler heads arranged in a row along a pipe, which may be as long as 1,000 feet or longer, which progressively moves in a row across a farmer's field.
Such sprinkling systems provide much more benefit per gallon of water applied to the crops than merely sending the water down the furrows. Each such sprinkler system may irrigate many acres of crops. Large farming operations may include many such irrigation systems watering hundreds or thousands of acres.
Importantly, the timing and the duration of irrigation is important. For example, it may be necessary to operate some sprinkler systems during the hours of the night when evaporation will be at a minimum. Furthermore, many sprinklers may be located quite some distance from the farmer's home or office. For these reasons, and for convenience of operation, many sprinkler systems may be remotely operated or employ automatic systems to control their operation.
The control of the flow of water through the sprinklers is effected by one or more valves which include an automatic operation mechanism. The valves typically used are generally referred to as "butterfly valves" which are operated between fully opened position and a fully closed position by rotating the valve stem about 90.degree..
In the past, it has been customary to utilize electric motors in cooperation with a series of gears and/or chains to rotate the valve stem. The use of electrical motors allows electrical control circuits to be used which may be conveniently programmed by the farmer to operate the valves and other irrigation equipment. Thus, the farmer is provided with the ability to remotely, and even automatically, irrigate a predetermined area on his farm with a predetermined amount of water.
While such automatically operated valves have many advantages, it is clearly impractical for the farmer to check the condition of each valve before it is operated. Importantly, such irrigation valves must operate reliably under harsh conditions where dust, dirt, extreme temperatures, and moisture tends to damage their electromechanical components. The presence of such contaminates and harsh environmental conditions causes many valves and valve operators to wear out quickly or be damaged.
It is current practice in most conventional irrigation systems to employ a valve which is operated by a small electric motor connected to the valve by way of plastic gears or gears and a metal drive chain. The typical motor widely used on smaller pipes (e.g., two to four inch diameter pipes) is a one-eighth horse power electric motor. The gears associated with the motor are generally fabricated from a plastic such as nylon or teflon.
Unfortunately, many motors used in prior art devices do not have adequate safety shut-off mechanism. As a result, if dirt or other types of obstructions enter the gears or the valve, the motor continues to turn until either the motor is damaged or the gears are rendered unusable.
Thus, the prior art devices are in need of regular maintenance, repair, and/or replacement in order to keep the irrigation system constantly in working order. A further difficulty with the prior art devices is that the parts used therein are often not generally available as replacement parts.
Aggravating this problem is the fact that every manufacturer adopts a different configuration for the shape of the valve stem and the mounting holes on the head of the valve such that the valves of each manufacturer require an operation system adapted for use with that particular valve.
Furthermore, manufacturers will often change the configuration of such parts periodically to require the farmer to purchase entirely new replacement items. Thus, it is often necessary to replace the entire valve operator at a substantial expenditure of money and time. The situation also leads to the situation where a farmer may have, for example, ten automatically operated valves on his farm each requiring different replacement parts.
Additionally, in an effort to shield the previously available devices from the effects of contaminants, some are housed in sealed cabinets. However, sealing the motor and its associated components in a cabinet often results in problems with condensation on the interior of the cabinet resulting in corrosion of the components. Additionally, the inclusion of a sealed cabinet increases the cost and complexity of the valve operator.
An additional drawback inherent in the previously available devices include the fact that no structure is provided the farmer which allows easy manual opening and closing of the valve should the valve operation system become disabled due to damage or a power failure.
Also, an appropriate valve closing time is critical to proper operation of an irrigation system because closing a valve too rapidly results in a pressure buildup which may burst a pipe. Accordingly, with previously available devices it is necessary to maintain a supply of different motors each having different rotation speeds or a supply of various sized gears and chains in order to obtain the proper closing time for the valve.
From the perspective of the farmer or the field service representative charged with repairing and maintaining a plurality of sprinkler systems scattered over perhaps an area covering hundreds of miles, the nonstandardization of parts among the different valves and operation systems presents a great disadvantage. Because of this nonstandardization, a large inventory of different replacement parts must be carried about in the field vehicle at all times since quick, around-the-clock repair service is the rule during the irrigation season.
In view of the foregoing, it would be an advance in the art to provide an irrigation valve operation system wherein either a single or a few different embodiments may be adapted for use with a plurality of differently configured valves whereby the need to keep on hand a plurality of different replacement parts for the embodiment is eliminated. It would also be an advance in the art to provide such an irrigation valve operation system which is readily interfaced with existing control systems. It would be a further advance in the art if the irrigation valve operation system made use of easily obtainable or easily fabricated replacement parts.
In addition to the foregoing, it would also be an advance in the art to provide an irrigation valve actuation system which is less susceptible to damage than previously available devices and which need not be completely enclosed in a sealed housing to provide reliable service. It would be a still further advance in the art to provide an irrigation valve actuation system which requires less maintenance than previously available devices performing similar functions and which may be adapted to be used with a range of valves of different sizes and capacities.